How can I create an enormous crater?

My world has a huge crater (4400 miles in diameter) on a world that's roughly earth equivalent (so a circumference of 25000 miles). The native population doesn't need to know how it was formed but it would be nice if the world creator did! Around the edge is a ring of islands, inside and outside there's nothing but the sea.

I've been thinking about the crater from the meteoroid which wiped out the dinosaurs. I believe it's 180 km in diameter, obviously, this is far too small. I'm not sure a planet could survive an impact from something almost ten times the size (apocalyptic isn't an issue but the planet needs to survive and go on to create life afterward).

I've thought about volcanoes but I'm not sure that would create the shape I'm looking for.

I can resort to magical means as a last resort but I'd really rather keep this real world.

Ideally, I would like the crater to start in the polar regions and stretch down well towards the equator (almost like the death star) so there is a vast range of islands. It does not need to be particularly deep so doesn't need to go anywhere near the planet's core.

Could a crater this size occur without godlike intervention? If so how?

posted over 9 years ago

Liath‭

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